You can't get your 28.8 Kbps modem to connect at anywhere near its top speed? You get disconnected at random times for no apparent reason? Maybe you have trouble establishing a connection to begin with.

If any of this sounds familiar, you're probably the victim of line noise. In general usage, the term line noise can refer to any unwanted signal that finds its way into your line or a loss of signal that should be there.

How line noise causes problems

When you call your Internet service provider (ISP), a local bulletin board, or even a friend's computer, your modem will negotiate with the other modem and attempt to make the fastest possible connection. The reason you may get a slower-than-expected rate is that faster connections are more error-prone. If, during this negotiation, it appears that a 28.8 rate will allow too many data errors, the modems will adjust to a slower, more reliable rate. If the connection is too noisy at any speed, one of the modems may terminate the connection.

The good news is that depending on the cause, you might be able to improve the quality of a noisy connection. Let's take a look at some of the more common causes of line noise and discuss ways to deal with it.

Is it really line noise?

Slow modem speeds aren't always the result of line noise. Before you reach a diagnosis of "line noise," you'll need to rule out other problems. First, make sure you've configured your modem correctly. If you've been using the modem with good results, you're probably OK. Otherwise, call your ISP's technical support department and ask for help setting up a workable configuration.

Now, test the quality of your connection. To do this, you'll need a terminal communications program that allows you to issue modem commands while you're connected. In Windows 95, you can use the Hyper Terminal program. You can access Hyper Terminal by going to your Windows Start menu and selecting Programs/Accessories/ HyperTerminal. If you're a Windows 3.x user, you can use a shareware program called NetTerm, which you can download from ftp://ftp.ncsa.uiuc.edu/Mac/Telnet/Telnet2.6/
Telnet2.6UserGuide

To test the connection, use the terminal communications program to call your ISP. When you're connected, enter three plus signs (+++). Then issue the AT%Q command. The modem will return a number between 1 and 127, which indicates the level of noise currently on the line. A reading of 15 or lower means you're in good shape regarding line noise, so the problem probably lies elsewhere. A reading of 50 is high enough to put you in danger of getting disconnected.

Where does the noise come from

At this stage, if you're sure you have line noise, the next step is to determine what's causing it. A good test is to call a few local bulletin boards in different telephone exchanges. Getting good connections here will establish that the noise isn't originating in your own line.

If noise shows up in connections to other numbers, look for things around the house that might cause a problem. The flat type of wire that runs from your wall to the modem, often called silk cable, isn't particularly good for data transmission and can allow the signal to degrade if the cable is too long. The usual recommendation is not to use a length more than eight feet. If yours is longer, consider moving your computer close enough to the phone jack to allow a shorter wire.

Try disconnecting other phones on the line. They can cause noise, especially if they have features that draw power when the phone is hung up, such as a LED display. Electrical devices close to the phone line can also interfere with the signal. Unplug any such devices, and if you see an improvement, move the device that seems to be causing the problem away from the phone line. In addition, a line noise filter -- a small device that plugs into your phone line -- is a possible solution for line noise. You can purchase a line noise filter at your local computer or electronics store. However, buying a filter should be a last resort simply because a filter can't solve all line noise problems.

Line testing

You can call your local telephone company and ask it to test your line. Some companies may be more agreeable than others, but if you're sure nothing inside the house is at fault, it can't hurt to ask.

The Federal Communications Commission (FCC) requires your phone company to maintain a minimum level of quality. The problem with line noise is that the FCC's specifications aren't high enough to guarantee error-free data connections at high modem speeds. Remember, the original purpose of the telephone system was to provide service for voice calls, and this carries with it a far lower threshold of technical quality than data transmissions require.

If testing shows the quality of your line falls within the FCC's requirements, your phone company has no real incentive to go to the expense of upgrading it. If the phone company fails to help, you can always file a complaint with the FCC at its Web site, located at www.fcc.gov

Outside the house

If you haven't resolved your line noise problem, your next step might be to wonder if it originates with your ISP. This is certainly possible, but in such a case, you can be sure your ISP is aware of it; other users will have already flooded your ISP with complaints, and your ISP will be working hard to get the problem cleared up. If you call your ISP, the technical staff may tell you whether there's a line noise problem, and if not, they might have some suggestions to help you deal with it.

The telephone company's switching equipment is another possible source of noise. As is the case with line testing, if the switching equipment provides adequate quality under FCC regulations, the telephone company isn't likely to do much to improve it.

Nonetheless, FCC-compliant systems should consistently give you a reliable connection at 14,400 baud or higher. Increasing it as high as 28,800 baud can become problematic; such a high speed requires more bandwidth than some phone lines can handle. Some people may not be able to connect at 28,800 at all.

Other factors

Line noise can also be introduced by a phone line's proximity to power lines, transformers, or radio or television transmitters. If you can establish the source of interference from a transmitter, the FCC requires the radio or TV station to fix the problem.

Conclusion

In this article, we looked at some of the more common causes of line noise and ways to deal with it. Line noise can originate from a number of sources, but a bit of investigation and experimentation may prove helpful. Start with the simplest and closest-to-home possibilities, work your way outward from there, and you'll have a good chance of finding at least a partial solution.